public class zifu {//数据类型和变量
    public static void main(String[] args) {
 /*       String a="sd";
        System.out.println(a.length());
        int A=10;
        String B="";
        System.out.println(String(A+B));
        String s1=String.valueOf(10);
        System.out.println(s1);
        String sd="4";
        int sd2=Integer.parseInt(sd);
        System.out.println(sd2);
        double sd1= Double.parseDouble(sd);
        System.out.println(sd1);
        System.out.println(Long.parseLong(sd));*/
        /*type1
        int4
        short2
        long8
        double8
        float4
        char2
        boolean True and False
         */
        for (int d=0;d<10;d++)
        {
            if(d==5)
            {
                System.out.println(d);
                break;
            }
        }
//        int a=10;
//        int b=20;
//        double ab=a*1.0/b;
//        System.out.println(ab);
        int a=10;
        //相当于 a=a+20;
//        a+=20;
        System.out.println(a++);
        System.out.println(a);
        System.out.println(!true);
    }

}
